U.S. patent number 4,787,449 [Application Number 07/157,677] was granted by the patent office on 1988-11-29 for oil recovery process in subterranean formations.
This patent grant is currently assigned to Mobil Oil Corporation. Invention is credited to Lloyd G. Jones.
United States Patent |
4,787,449 |
Jones |
November 29, 1988 |
Oil recovery process in subterranean formations
Abstract
Oil recovery from a subterranean, oil-containing formation
having relatively highly permeable and/or fractured zones and
relatively low permeability zones is improved by first injecting a
predetermined amount of a plugging agent into the formation,
preferably inorganic, non-polymeric solids suspended in a fluid
such as drilling muds or bentonite or clay suspensions, that plugs
the face of the highly permeable and/or fractured zones of the
formation. Thereafter, injection of the plugging agent is continued
or in the alternative a displacing fluid at a flow rate and
pressure sufficient to initiate and propagate new fractures and/or
extensions of existing fractures in the formation. Thereafter, a
displacing fluid is injected into the formation at a pressure
sufficient to maintain the new fractures and/or extensions of
existing fractures open and displace oil from zones communicating
with the new fractures and/or extensions of existing fractures
toward a production well where it is recovered. Formation of the
new fracture and/or extensions of existing fractures enables
additional oil-containing zones in the formation to be swept by the
displacing fluid thereby improving oil recovery.
Inventors: |
Jones; Lloyd G. (Dallas,
TX) |
Assignee: |
Mobil Oil Corporation (New
York, NY)
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Family
ID: |
26721241 |
Appl.
No.: |
07/157,677 |
Filed: |
February 19, 1988 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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44166 |
Apr 30, 1987 |
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Current U.S.
Class: |
166/259; 166/270;
166/271; 166/281; 166/283 |
Current CPC
Class: |
E21B
43/164 (20130101); E21B 43/17 (20130101); E21B
43/2405 (20130101); E21B 43/247 (20130101); E21B
43/261 (20130101) |
Current International
Class: |
E21B
43/25 (20060101); E21B 43/247 (20060101); E21B
43/17 (20060101); E21B 43/24 (20060101); E21B
43/26 (20060101); E21B 43/16 (20060101); E21B
043/20 (); E21B 043/247 () |
Field of
Search: |
;166/271,274,281,283,308,292,272,259 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Rogers, Walter F., "Composition and Properties of Oil Well Drilling
Fluids", 3rd Ed., Gulf Publishing Co., Houston, Tex., 1963, pp.
404, 405..
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Primary Examiner: Novosad; Stephen J.
Attorney, Agent or Firm: McKillop; Alexander J. Gilman;
Michael G. Miller; Lawrence O.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of my co-pending
application Ser. No. 044,166, filed Apr. 30, 1987, the entire
contents of which is incorporated herein by reference.
Claims
I claim:
1. A process for recovering oil from a subterranean, oil-containing
formation having at least one injection well and a spaced-apart
production well in substantial fluid communication with said
formation and further having relatively high permeability and/or
fractured zones and relatively lower permeability zones,
comprising:
(a) injecting a predetermined amount of a plugging agent into the
formation via the injection well which preferentially enters the
highly permeable and/or fractional zones and plugs the face of said
zones;
(b) continuing to inject said plugging agent into the formation at
a flow rate and pressure sufficient to initiate and propagate new
fractures and/or extensions of existing fractures in the formation;
and
(c) thereafter injecting a displacing fluid into the formation at a
pressure sufficient to maintain the new fractures and/or extensions
of existing fractures open and displace oil from zones
communicating with said new fractures and/or extensions of existing
fractures toward the production well where it is recovered.
2. The process of claim 1 wherein the plugging agent is inorganic,
non-polymeric solids suspended in a fluid.
3. The process of claim 1 wherein the plugging agent comprises a
drilling mud.
4. The process of claim 1 wherein the plugging agent comprises a
clay suspension.
5. The process of claim 1 wherein the plugging agent comprises a
bentonite suspension.
6. The process of claim 1 wherein the displacing fluid comprises
water, carbon dioxide, steam or a combustion front.
7. A process for recovering oil from a subterranean, oil-containing
formation having at least one injection well and a spaced-apart
production well in substantial fluid communication with said
formation and further having relatively high permeability and/or
fractured zones and relatively lower permeability zones,
comprising:
(a) injecting a predetermined amount of a plugging agent into the
formation via the injection well which preferentially enters the
highly permeable and/or fractional zones and plugs the face of said
zones;
(b) injecting a displacing fluid into the formation at a flow rate
and pressure sufficient to initiate and propagate new fractures
and/or extensions of existing fractures in the formation; and
(c) thereafter continuing to inject said displacing fluid into the
formation at a pressure sufficient to maintain the new fractures
and/or extensions of existing fractures open and displace oil from
zones communicating with said new fractures and/or extensions of
existing fractures toward the production well where it is
recovered.
8. The process of claim 7 wherein the plugging agent is inorganic,
non-polymeric solids suspended in a fluid.
9. The process of claim 7 wherein the plugging agent comprises a
drilling mud.
10. The process of claim 7 wherein the plugging agent comprises a
clay suspension.
11. The process of claim 7 wherein the plugging agent comprises a
bentonite suspension.
12. The process of claim 7 wherein the displacing fluid comprises
water, carbon dioxide, steam or a combustion front.
Description
FIELD OF INVENTION
This invention relates to a process for improving oil recovery from
a subterranean, oil-containing formation by initially selectively
plugging the face of permeable and/or fractured zones in the
formation with a plugging agent, continuing to inject the plugging
agent or in the alternative a displacing fluid to initiate and
propagate new fractures and/or extensions of existing fractures in
the formation and thereafter injecting a displacing fluid at a
pressure sufficient to maintain the new fractures and/or extensions
of existing fractures open and recover oil from zones in
communication with the new fractures and/or extensions of existing
fractures.
BACKGROUND OF THE INVENTION
A variety of supplemental recovery techniques have been employed in
order to increase the recovery of viscous oil from subterranean
viscous oil-containing formations. These techniques include thermal
recovery methods, waterflooding and miscible flooding.
Heterogeneous hydrocarbon containing subterranean formations, i.e.,
formations having relatively high permeability zones and relatively
lesser permeability zones, are difficult to efficiently flood by
secondary and/or tertiary oil recovery processes because fluids
preferentially migrate into the highly permeable zones in the
subterranean formations. This process is aggravated by natural or
accidental fracturing of the formation adjacent the injection well
since such fractures commonly occur only in one or a few of the
layers in layered formations. The migration described above is
undesirable when injecting treatment fluids into oil-containing
formations for the recovery of oil since the treatment fluids
channel through the highly permeable and/or fractured zones
bypassing the less permeable zones. The result is poor conformance
and flow profiles of the treatment fluid in the formation. The
hydrocarbons residing in the less permeable zones are not produced
and the overall yield of hydrocarbons from the formation is
reduced.
To increase the efficiency of formation flooding processes, the
highly permeable and/or fractured zones in subterranean formations
are plugged or partially plugged to prevent or educe migration of
treatment fluids into them and to divert treatment fluids into
adjacent, less permeable zones. In injection profile control
projects, polymeric materials have been used in liquid slurries or
suspensions to effectively enter and plug or partially plug the
highly permeable and/or fractured zones of the formation. Fluids
injected after such a treatment therefore move into unswept areas
or zones of the reservoir which results in increased oil
recovery.
Accordingly, it is a primary object of this invention to provide a
process for improving oil recovery from a subterranean,
oil-containing formation comprising first injecting a plugging
agent that is stable at very high temperatures and which is very
cheap in comparison to polymers into the formation that
preferentially enters the highly permeable and/or fractured zones
of the formation and plugs the face of said zones, continuing
injection of the plugging agent or in the alternative a displacing
fluid to form new fractures and/or extensions of existing fractures
in the formation and injecting a displacing fluid into the
formation at a pressure sufficient to maintain the new fractures
and/or extensions of existing fractures open and displace oil from
zones communicating with the new fractures and/or extensions of
existing fractures toward a production well where it is recovered.
Formation of the new fractures and/or extensions of existing
fractures enables additional oil-containing zones in the formation
to be penetrated by the displacing fluid for the recovery of oil
thereby improving oil recovery from the formation.
SUMMARY OF THE INVENTION
The present invention provides a process for improving oil recovery
from a subterranean, oil-containing formation having relatively
highly permeable and/or fractured zones and relatively low
permeability zones and penetrated by at least one injection well
and a spaced-apart production well in substantial fluid
communication with the formation. Initially, a predetermined amount
of a plugging agent, preferably inorganic, non-polymeric solids
suspended in a fluid such as drilling muds and bentonite or clay
suspensions, is injected into the formation via the injection well
which preferentially enters the highly permeable and/or fractured
zones and plugs the face of these zones. Thereafter, injection of
the plugging agent is continued or in the alternative a displacing
fluid to initiate and propagate new fractures and/or extensions of
existing fractions in the formation thereby creating additional
locations in the formation for the recovery of oil. Thereafter, a
displacing fluid in injected into the formation at a pressure
sufficient to maintain the new fractures and/or extensions of
existing fractures open and displace oil from zones communicating
with said new fractures and/or extensions of existing fractures
toward the production well where it is recovered.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides a process for improving oil recovery
from a subterranean, oil-containing formation having relatively
highly permeable and/or fractured zones and relatively low
permeability zones. The formation is penetrated by at least one
injection well and a spaced-apart production well in substantial
fluid communication with the formation. Initially, a predetermined
amount of a plugging agent is injected into the formation via the
injection well, preferably inorganic, non-polymeric solids
suspended in a fluid such as drilling muds and bentonite or clay
suspensions. The injected plugging agent preferentially enters the
highly permeable and/or fractured zones and plugs the face of the
highly permeable and/or fractured zones. The amount of plugging
agent injected into the formation will vary depending upon
formation characteristics and the degree of plugging desired.
Thereafter, injection of the plugging agent is continued or in the
alternative a displacing fluid until the injection pressure exceeds
the desired fracture extension or fracture initiation pressure in
an alternate layer of the formation to initiate and propagate new
fractures in the formation and extend many or all of the previously
plugged or partially plugged fractures. Injection of the plugging
agent or displacing fluid at the higher injection pressure and
sufficient flow rate is continued until the desired fracture
pattern is obtained depending upon the characteristics of the
formation. Thereafter, a displacing fluid is injected into the
formation via the injection well at a pressure sufficient to
maintain the new fracture and/or extensions of existing fractures
open and displace oil from zones communicating with the new
fractures and/or extensions of existing fractures toward the
production well where it is recovered. The injection pressure of
the displacing fluid must be sufficiently above the vertical
fracture gradient so as to maintain the new fractures and/or
extensions of existing fractures open and thus facilitate recovery
of oil from these zones. Displacing fluids can be any fluid which
effectively displaces crude oil from the formation, e.g., it can be
an immiscible, miscible, or miscible-like displacing fluid.
Suitable displacing fluids include steam, water, carbon dioxide or
a combustion front. Forming new fractures and/or extensions of
existing fractures in the formation enables additional
oil-containing zones in the formation to be penetrated by the
displacing fluid for the recovery of oil thereby improving oil
recovery.
In another embodiment of my invention, a displacing fluid is
injected into the formation that preferentially enters the high
permeability zones and oil is recovered until the high permeability
zones have been depleted. Thereafter, the present process of
plugging the face of the high permeability zones and thereafter
forming new fractures in other zones and/or extensions of existing
fractures in the formation in communication with oil-containing
zones from which oil is recovered.
Although the present invention has been described with preferred
embodiments, it is to be understood that modifications and
variations may be resorted to, without departing from the spirit
and scope of this invention, as those skilled in the art will
readily understand. Such variations and modifications are
considered to be within the purview and scope of the appended
claims.
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